ch1 Flashcards
what’s census and what are adv and disadv of it
measures or observed every member of a population
adv.
results give accurate result
disadv - time consuming
- hard to process large quantity of data
what’s sample and what are adv and disadv of it
it’s a selection of observations taken from a subset of the population of high is used to find out info about the population as a whole
adv. less time consuming
fewer people have to to respond
less data to process than in a census
disadv. data may not be accurate
sample may not be large enough to give info about small sub groups of the population
what are two types of raw data
Census
sample
what are individual units of a population known as
Sampling units
what are sampling frames
a list of sampling units
what are the three methods of random sampling
simple random sampling
systematic sampling
stratified sampling
what is simple random sampling with adv and disadv
a sample of size n is one where every sample of size n has an equal chance of being selected
adv
-free of bias
- easy and cheap
disadv
- not suitable for large samples
- sampling frame needed
what’s systematic sampling and what are adv and disadv of it
the required elements are chosen at regular intervals from an ordered list
ex. if there’s a sample size of 20 was required from a population of 100, you could take every fifth person 100/20
adv.
- simple and quick to use
- suitable for large samples
disadv
- sampling frame is needed
- bias introduced if sampling frame is not random
what’s stratified sampling and what are adv and disadv of it
the population is divided into mutually exclusive strata and a random sample is taken from each.
adv
- sample accurately reflects population
disadv
- population must be clearly classified into distinct strata so it’s time consuming
what’s the formula for finding the number sampled in a stratum in stratified sampling
number in stratum/number in population x overall sample size
what are two types of non random sampling
Quota sampling
Opportunity sampling
what’s Quota sampling and what are adv and disadv of it
an interviewer or researcher selected a sample that reflects the characteristics of the whole population
adv
- no sampling frame needed
- efficient
- cheap
- wuick and easy
- allows easy comparison between different groups within a pop
disadv
- can be bias
- population must be divided into groups which is costly and inaccurate
- increasing scope of study increases number of groups sooo time consuming.
what’s Opportunity sampling and what are adv and disadv of it
it consists of taking the sample from people who are available at the time the study is carried out and who fit the criteria they are looking for
adv .
- easy to carry out
- not expensive
disadv.
- unlikely to provide a representative sample
- highly dependent on individual researcher
in opportunity sampling why is it unlikely to provide a representative sample
sample is likely to be biased towards the people who they collect data from at that day
what are the 4 types of data
Quantitative data
Qualitative data
Continuous variable
Discrete variable
what’s Quantitative data
it’s data that’s associated with numerical observations
ex. number of a shoe size
what is Qualitative Data
data that’s associated with non-numerical observations
ex. can’t give a number to a hair colour (red, blue, brown)
what’s continuous variable
a variable that can take any value in a given range values
ex. then can take any value like 2seconds, 2.1 seconds, 2.01seconds
what’s discrete variable
a variable that can only take specific values in a given range
ex. number of girls in a family cuz u can’t have 2.5 girls
what does the large data set data ask for
daily mean temp
daily total rainfall
daily total sunshine
daily mean wind direction and wind speed
daily maximum gust
daily maximum relative humidity
daily mean cloud cover
daily mean visibility
daily mean pressure
what’s an outlier
an outlier is an extreme value that lies outside the overall pattern of the data
